1. Field of the Invention
This invention generally relates to connecting integrated circuit (IC) devices to a substrate within a computer system. In particular, an overlay element is provided such that the input/output (I/O) contact points on the chips can be rearranged, thereby allowing different interconnect configurations.
2. Description of Related Art
Generally, ICs are placed flat, i.e. the largest surface is placed on a planar board or circuit card. More specifically, the plane of the IC is parallel with the plane of the circuit card on which the chip is mounted. These integrated circuits are then electrically connected to the circuitry on the card by using known methods, such as wire bonding or direct chip attach (DCA) technology. Additionally packaged ICs such as surface mount technology (SMT) or pin-through-hole (PTH) chips are also placed flat on the printed circuit board and then electrically attached thereto.
Interconnect elements for attaching chips to substrates, or the like are also known. IBM Technical Disclosure Bulletin "Transmission Line Right Angle Connector" shows an interposer, having matching wiring, is disposed between perpendicular chip carriers. U.S. Pat. No. 5,050,039 describes a chip mounting arrangement wherein chips are attached, on one side, to a heat sink and the I/Os are connected to vertically disposed interconnect boards. A flex circuit is used to connect the interconnect boards to a motherboard.
Additionally, it is known to perpendicularly mount, with reference to a corresponding substrate, a plurality of chips in a support member, as shown in U.S. Pat. Nos. 4,982,264 and 5,059,557. In these arrangements electrical conductors are disposed in a surface of the support member to contact bonding pads located on the chips. Further, chips can be mounted perpendicularly with respect to a substrate in a "free standing" configuration. U.S. Pat. Nos. 4,922,378 and 5,031,072 describe a base plate having channels therein for supporting perpendicularly mounted integrated circuits. The ICs are electrically interconnected to the base plate through pads on the IC and base plate. The base plate and IC assembly is then electrically interconnected to an underlying planar surface by interconnecting a plurality of baseboard pads and connector pads. IBM Technical Disclosure Bulletin "Vertical Chip Packaging" discusses mounting chips perpendicularly on a substrate. The ICs are either placed in a channel in the substrate, or supported by a foil "foot" bonded to the back of the chip. The foot can also be used to supply electrical power to the chip. Foil "fingers" are then used to electrically interconnect the chip signal I/Os to the substrate. It can be seen that conventional perpendicular chip mounting requires placement of I/Os at a specific location on the chip. In the prior art, this placement of I/Os occurs at the chip fabrication level and requires custom made chips be acquired from chip manufacturers. Of course, a great deal of packaging flexibility is lost if specific chips must be special ordered from the manufacturer. Further, availability problems may also exist if standard "off the shelf" types of chips can not be purchased and used in the desired packaging configuration. Therefore, it would be advantageous to have a means of reconfiguring any type of chip to meet the desired packaging configuration.